La Gazzetta dello Sport reported Wednesday that Henao, who has not raced since the Tour of Oman, had “anomalous values” as part of internal team controls. Sky quickly released a statement on its website to spin the story.

“In our latest monthly review, our experts had questions about Sergio’s out-of-competition control tests at altitude — tests introduced this winter by the anti-doping authorities. We need to understand these readings better,” team principal Dave Brailsford said in a team release.

“We contacted the relevant authorities — the UCI and CADF [the UCI’s Cycling Anti-Doping Foundation] — pointed to these readings and asked whether they could give us any insights. We’ve also taken Sergio out of our race program whilst we get a better understanding of these profiles and his physiology.”

It was not revealed exactly what the “anomalies” were, but it appeared that the questions arise from internal team controls, and not the biological passport, which monitors athletes’ blood levels.

Sky confirmed Henao underwent WADA-accredited controls during a winter trip to Colombia, but did not specify if it was linked to those tests. A biological passport violation could lead up to a two-year ban for a first-time offense.

There was not yet an official response from the UCI on Wednesday morning.

Brailsford insisted the inconsistencies could stem from the effects of altitude. Henao, like many of the Colombians in the peloton, lives and trains at high altitude. His hometown is Rionegro, near Medellín, at an altitude of 7,000 feet.

Brailsford said the team wants to further study the effects of altitude on biological profiles.

“Our own understanding is limited by a lack of scientific research into ‘altitude natives’ such as Sergio,” Brailsford said. “We are commissioning independent scientific research to better understand the effects of prolonged periods at altitude after returning from sea level, specifically on altitude natives.”

Sky said Henao will be sidelined “at least eight weeks” while the team completes its assessment.

While Sky tried to downplay the news Wednesday, the implications are huge, both for the team and for Henao.

The 26-year-old Henao, whose younger cousin, Sebastian, joined Sky for 2014, was expected to start the Tour de France as a support rider for defending champion Chris Froome.

The climber is also part of a new wave of Colombian riders making a huge impact on the international peloton. Just this past week, Carlos Betancur (Ag2r-La Mondiale) won Paris-Nice and Nairo Quintana (Movistar) rode to second at Tirreno-Adriatico.

One reason cited by some for the Colombian resurgence is the reduced abuse of EPO inside the peloton, which some assume restores the competitive advantage that many Colombians, most of whom live and train at altitude, would enjoy with a naturally higher hematocrit level that comes with altitude.

Despite racing in Europe, many of the top Colombians return home for extended periods of time during the racing season, a decision that raises eyebrows in some circles. Some are dubious whether controls are as vigorous in South America as they are in Europe.

Brailsford insistence that extended periods at altitude alters biological passport numbers has also been the subject of an ongoing debate. There are clear benefits of training at altitude, as evidence by the parade of top GC contenders spending weeks on the Spanish island of Tenerife, including Sky, but how that is reflected and interpreted in the biological profile remains a contentious issue.

Sky, too, desperately wants to avoid any hint of a scandal, both to protect its sponsorship backing as well as its reputation as a “clean team.”

Any doping scandal involving a Sky rider would have devastating effects on the team. Sky already saw how much bad press can be generated with the disciplinary case involving John Tiernan Locke, who is facing a potential ban for biological passport anomalies in the season before he joined Sky.

Sky is walking a tightrope between transparency and legitimacy, as Brailsford said, “We want to do the right thing, and we want to be fair. It’s important not to jump to conclusions.”

Andrew Hood

Andrew Hood cut his journalistic teeth at Colorado dailies before the web boom opened the door to European cycling in the mid-1990s. Hood has covered every Tour de France since 1996 and has been VeloNews' European correspondent since 2002.